Marginal abatement cost curve (MACC)
A ranking of abatement options by cost per tonne, used to sequence action from cheapest to most expensive.
A MACC orders interventions by their cost per tonne of emissions avoided or removed. Options below zero save money while reducing emissions; options higher up the curve require subsidy, regulation or a carbon price to proceed.
The curve is a communication device as much as an analytical one. It makes the trade-offs visible and shows how much abatement is available at a given price, which is useful for target setting and policy design.
Its weaknesses are structural. Options are not independent — deploying one changes the cost of another — and the curve is static, ignoring how costs fall with scale. Reading it as a fixed menu rather than a snapshot misleads.
Frequently asked questions
Why do some options have negative cost?
Because they save money through lower energy or input use while also reducing emissions.
Are MACCs used for removals?
Increasingly, though removals are harder to cost because they depend on storage duration and monitoring obligations.